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28 Cards in this Set

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What are the vitamers of Vit E and how do their structures differ?
a-b-g-d tocopherol.
Two rings. Important on is conjugated & with one OH and multiple CH3 groups.
a = 3 CH3
B, g = two
d = one
activity roughly correlates to # of CH3 groups
What is a free radical?
A compound that can exist independently that has one or more unpaired electrons
What are some examples of free radicals?
O2!
Superoxide
RO - alkolyl
ROO - peroxyl
OH - hydroxy
How is a lipid peroxide formed?
LH --> L• + H
L• + O2 --> LOO•
What initiates lipid oxidation?
OH•, RO•, ROO• : a number of free radicals
Where do initiators come from?
OH• : gamma ray fission of H20
and
indirectly from LOOH and superoxide
Draw the cycle of oxidation!
See book
What is a hydroperoxide?
LOOH (or ROOH)
What (in words) is the Haber-Weiss rxn? What is required?
The pathway that forms a hydroxy radical (OH•) from a hydroperoxide (ROOH)

Catalyzed by Fe2+
Requires superoxide
Write the Haber-Weiss reaction
ROOH + O2-• ---> OH• + RO- + O2
(Fe)
How does Vit E terminate the chain reaction?
OH group reacts w/ROO•
Why is Vit E stable?
Conjugated ring: unpaired electron is delocalized throughout ring structure; more stable, less reactive arrangement.
How is Vit E regenerated?
It is regenerated from ascorbate. H gets donated. Ascorbate --> semi dehydro ascorbate. (Which then reacts w/itself "disproportionation")
What is the term called when Vit C regenerates Vit E?
Quenching
What is Malonaldehyde? Why is it so bad?
A bi-product of lipid oxidation. O=CH-CH2-CH=O
Two aldehyde groups are very reactive with free amines; crosslinking (polymerization) can occur.
Why do we care about lipid peroxides anyways?
Lipids are in membranes.
• disruption of hydrophobic nature of membranes "fragmentation"
• loss of membrane bound enzyme activity
• formation of aldehyde/ketone groups ie malonaldehyde
Lipid (hydro)peroxides are being formed all the time by us; How are they then metabolized? (1st rxn & enzyme)

(LOOH)
(1) RXN with glutathione (GSH):
LOOH + 2GSH --> LOH + GSSG +H2O
forms lipid alcohol (b-ox)

Enzyme = glutathione peroxidase
Co-factor = Se!!!
How does adequate Se reduce the load of Vit E required?
LOOH can go either the route of Haber-Weiss and form additional free radicals, or it can be metabolized via Se-requiring pathway. If added free radicals, more Vit E required to quench.
What is GSSG?
Oxidized glutathione (GSH)
What happens to GSSG created during LOOH metabolism?
It gets regenerated (reduced) back:
GSSG + NADPH+H --> 2 GSH + NADP
Enzyme: glutathion reductase
Co-factor: RF
What is glutathione? (What is it made of)?
Tripeptide containing cysteine (sulfur group).
Se is known to ameliorate need for Vit E. Sulfur amino acids do too. Why?
LOOH + 2GSH --->
GSH: sulfur-containing tri-peptide (cysteinyl).
Draw the "unified anti-oxidant action" schematic- for the fate of LOOH
Draw it; see notes.
What causes most Vit E deficiencies?
Fat malabsorption from disease.
Signs of Vit E def?
Susceptible populations?
Signs include spinal cord degeneration, swollen axons, accumulation of organelles.

Susceptible population: premies
What deficiency sign is found in premies?
Hemolytic anemia. It's a decrease in RBC survival without increased production - premature lysis.
Vit E Biochemical method of assesment?
Most common: plasma or blood serum a-tocopherol status
Function test of Vit E status?
Two main ones:
Erythrocyte hemolysis in vitro when exposed to H202 - measure time to lysis
and
Breathe ethane & pentane (which are FA ox products)